Ash traces hint at cave cuisine 1 million years ago

You could call it the original baptism of fire: the moment hominins first began controlling flames. There is now evidence that moment came at least 1 million years ago, a finding that will reignite the debate over whether human anatomy was changed forever by cooking.

There is a huge discrepancy between the timing of these changes in hominin anatomy and the archaeological record of fire, says Chazan. "My heavy bias has always been that humans didn't control fire until much later – until now." In fact, he says, earlier evidence of fire does exist, you just have to look for it in the right way.

Ash and bone

There are no obvious hearths in South Africa's Wonderwerk cave, but when Chazan, Francesco Berna and Paul Goldberg, both at Boston University, used microscopic analysis to study the sediments on the cave floor, they found evidence of ash and traces of burnt bone in layers that formed 1 million years ago. The burnt remains are 30 metres from the present entrance to the cave, so they are unlikely to represent the action of wildfires, says Chazan.

It is more likely that hominins – probably Homo erectus – carried fire into the cave, he says. "There's no evidence to suggest they were creating fire. I think they were making occasional and opportunistic use of natural wildfires." The burnt bone fragments – including bits of tortoise bone – suggest, but do not prove, that H. erectus was cooking food, he adds.

Wrangham calls the work an "exciting breakthrough". "There are other sites in Africa, more than 1 million years old, that now bear re-examination," he says.

The new study is not final proof of Wrangham's cooking hypothesis, though. Chazan points out that the tiny traces of fire in the cave stand in contrast to the extensive ash deposits from fire found in much later sites of human occupation. That suggests H. erectus was not using fire regularly, or routinely cooking food – despite its small teeth and large brains. "The problem is fascinatingly awkward," admits Wrangham.

Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1117620109

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